1. Field of the Invention
The present invention relates to a method for enhancing in-situ oil production from oil shale, oil sand, asphaltic crude oil, or other high viscosity crude oil formations. This method employs delivering energy in the form of concentrated solar flux to these formations in order to passively heat them and thereby increase their oil production.
2. Description of the Related Art
The heating of oil shale formations has been demonstrated in the prior art as the critical component of the in-situ production of oil from oil shale. Heating of the formation has also been shown in the prior art to enhance production yields from certain oil-bearing zones containing viscous crude oils such as oil sand formations and asphaltic crude fields.
Approximately two trillion (2,000,000,000,000) barrels of potentially recoverable oil shale resources are located in the eastern and western states of the United States. The western states alone contain approximately 62% of the world's known oil shale deposits. However, the term “oil shale” is not an accurate description for these potential energy resources. In fact, they are not truly petroleum oil nor do the rock formations consist of shale. The organic material is primarily kerogen, not oil, and the kerogen bearing rock strata are often comprised of a relatively hard material called marl. The kerogen can be processed into a petroleum-like substance by the introduction of heat.
Unlike naturally occurring petroleum oil deposits, the organic kerogen deposits have not been through the “oil window” of heat. This “oil window” of heat is the final step in the natural development of petroleum oil. These shale formations are often located too shallow in the earth to have been subjected to sufficient temperatures to complete the process of transformation into the liquid oil form.
The two most common techniques currently employed for extraction of kerogen from the oil shale are surface mining and then heating the mined shale (also referred to as retorting techniques) or in-situ heating production techniques.
Traditional retorting techniques present several problems and limitations. Traditional retorting techniques remove the kerogen bearing material or “shale” using conventional open pit or room and pillar mining equipment and processes. The shale is crushed and heated or retorted in a surface heater or retort resulting in the recovery of kerogen oil, a petroleum-like liquid. The costs associated with the mining processes and the inefficiencies of the retorting equipment limit the economic viability of traditional retorting processes. Also, post-retort residual rock fines and other tailings from the mining process have a significant adverse environmental impact. The volume increase of spent shale, due primarily to the crushing prior to heating, can be as high as 30%. This increase in volume results in an inability to return all of the residual materials to landfill in the mines from which they originated.
The other common technique involves in-situ heating of the formation. This technique differs depending on whether the formation is kerogen bearing oil shale or is viscous crude oil bearing oil sand or asphaltic crude field. In-situ heating techniques also present several problems and limitations.
The In-situ Conversion Process (ICP) is an emerging technology in which heat is added underground to a kerogen bearing formation over a period of years. This heat slowly converts the kerogen into hydrocarbon gases and kerogen oil. Then these gases and kerogen oil are recovered using conventional oil production techniques.
Using ICP, electric or gas heaters are inserted into vertical wells surrounding a producing well and the heaters are used to heat the ore-bearing strata. Due to the slow heating involved with this technique, the quality of the kerogen oil produced is increased compared to retort processes. Unfortunately, a large amount of electrical energy or gas is needed to heat and to maintain the formation at a sufficient temperature. In addition to the fuel costs, the remote location of these types of oil producing fields necessitates construction of pipelines or electrical transmission infrastructure to bring sufficient gas or electricity to these sites. Without relatively high oil prices to support the additional operation and capital construction costs, these extraction techniques can be cost prohibitive.
The current practice for extraction of bitumen from oil sands consists primarily of surface mining and heating. This process has similar limitations to the oil-shale mining techniques discussed above. Specifically those limitations involve the mining and heating costs which limit the economic viability of the process.
The in-situ heat requirement for oil sands is different than for oil shale since the bitumen in oil sand consists primarily of a highly viscous crude oil that needs to be heated to improve its flow characteristics. Currently, steam flood techniques are the preferred in-situ heating technique for oil sand deposits. When steam enters the formation, the steam gives up heat and condenses in the formation to form water. Once the bitumen has been heated in-situ, a mixture of bitumen and water can then be recovered using conventional oil production techniques. These in-situ techniques are economically limited due to the cost of energy to create steam and the need for large quantities of water.
The present invention addresses these problems by employing a readily available source of energy, i.e. sunlight, to heat the formations. The invention involves a method to enhance oil shale, oil sand, asphaltic crude oil, or other high viscosity crude oil production by efficiently and effectively converting concentrated energy in the form of solar flux into useable forms of heat energy that can be employed to heat the formations.
Use of solar energy to provide the heat required for these operations allows for a cost-effective method to enhance oil production without the current practice of burning fossil fuels or use of electrical heating. The present invention employs solar blackbody waveguide technology, acting as a solar-powered heating element, to directly heat the geological strata of these ore-bearing and oil-bearing formations.